1. Field of the Invention
The present invention relates to processes for the preparation of polyimide-isoindroquinazolinedione and precursor thereof.
2. Prior Art
Hithertofore, polyimide-isoindroquinazolinedione and polyimide have been used as heat-resistant electric insulation materials and also as constructive materials for parts of electronic instruments such as interlayer insulation membranes for semi-conductors, surface protection coating films, -ray shield films and the like. These polymers have been utilized generally in the following manner:
Their precursor solutions were applied onto substrates such as those of silicon wafer, glass plate, metal plate, etc. to form a coated film, which was then subjected to heat-treatment to obtain a partially imidated film; a resist was formed on the film in a desired pattern; the resulting resist was dipped in an etching solution to dissolve and remove unnecessary portions; and the etched resist film was then peeled off and the film subjected to heat-treatment again, thereby being completely cured to form various type of films.
As the above polyimide-isoindroquinazolinediones, the following compounds are already known from prior art, for example, Japanese Patent Publication (Kohkoku) Sho 60-43370 Official Gazette: those obtained by reacting acid dianhydrides such as 3,3',4,4'-biphenyltetracarboxylic acid dianhydride or the like, diaminoamide compounds such as 4,4'-diaminodiphenylether-3-carboxylic acid amide or the like, diaminosiloxanes such as 1,3-bis(aminopropyl)tetramethyldisiloxane or the like, and diamines.
As said polyimides, in addition to those used in the form of the precursor solution mentioned above, polyimides in which the imidation has already been completed and which are soluble in polar solvents such as N-methylpyrrolindone, etc. are known from for example, Japanese Laid-open (Kokkai) Patent Application Sho 61-4700 Official Gazette.
The conventional polyimide-isoindroquinazolinediones as disclosed in the above mentioned Japanese Patent Publication Sho 60-43370 Official Gazette have such a defect as not being application to devices not having a heat-resistance level beyond 250.degree. C., because said polyimide-isoindroquinazolinediones require full curing temperatures exceeding 250.degree. C., practically a temperature of 300-400.degree. C. In addition these conventional polyimide-isoindroquinazolinediones have a higher modulus of elasticity and there is the risk of crack occurrence and peeling off from base materials.
On the other hand, many of the conventional polyimides also requires temperatures exceeding 250.degree. C. for their full curing. Although some polyimides can be cured at a temperature below 250.degree. C., generally, polyimides have a fault of their tensile strength being lower. Further, as polyimides capable of being treated at a temperature below 250.degree. C., there are the polyimide resins having already completed their imidation as disclosed in Japanese Kokkai Patent Application Sho 61-4700 Official Gazette. However, when such polyimides are dipped into an etching solution for the dissolution and removal of unnecessary portions as aforementioned, it is known that speed thereof is very slow as compared with the resins in which only the partial imidation has proceeded [see "Kino Zairyo" (Functional Materials) Published on May and June, 1984]. Accordingly, such completely imidated polyimides cannot be employed for the uses requiring etching treatment as mentioned before.